A 29-year-old burned-out corporate assistant manager who dies from severe overwork and regresses nine years into the past into his 20-year-old trainee body at UA Entertainment. Pragmatic, deeply cynical about showbiz, and driven by a relentless focus on deliverables, his sole existential imperative is satisfying the KPI System's objectives to resurrect his deceased sister. He views the idol industry through the lens of project management, risk analysis, and corporate resource allocation, secretly aiming for an early retirement once his sister is restored. Powers: Governed by the KPI System Interface, granting real-time status diagnostics, performance quests, and targeted attribute growth. Possesses advanced vocal adaptability, high-tier music arrangement, sharp lyrical composition, and tactical crisis management skills derived from nine years of high-stress corporate negotiations.

Renowned as the "Center Emperor," Jeho possesses top-tier natural visuals and magnetic stage charisma. Initially perceived as aloof and prone to friction with perfectionist trainees, his defensive exterior hides an intense fear of inadequacy under broadcast pressure. Guided by Iwol's structured training and emotional calibration, he matures into Spark’s undeniable visual and performance anchor. Powers: S-Tier Visual and Natural Charm stats; exceptional stage presence, rapid choreography memorization, and high-impact center performance synchronization.

A gentle, fifth-year veteran trainee who serves as the emotional foundation of the trainee dorms. Despite possessing remarkable vocal talent, years of psychological abuse and sabotage by senior singer Jang Junho left him with crippling stage anxiety and deep self-doubt. Iwol’s calculated intervention shatters his trauma, restoring his self-worth and establishing him as the main vocal powerhouse of Spark. Powers: High-tier emotive vocal control, wide vocal range, acoustic pitch accuracy, and stabilizing harmonic support during live broadcasts.

A fiercely disciplined, uncompromising perfectionist whose relentless work ethic sets the baseline for the entire trainee lineup. He harbors zero tolerance for half-hearted efforts, which initially causes friction with less experienced members. Even when concealing a debilitating chronic ankle injury, his commitment to technical precision never falters. Powers: Elite dance execution, technical choreography synchronization, sharp rhythmic isolation, and relentless physical conditioning.

A radiant, naturally charming trainee whose bright disposition masks a serious artistic drive. Recognizing his raw creative intuition, Iwol takes him under his wing, training him in song composition, track structuring, and lyric writing, transforming him into an essential contributor to Spark’s self-produced discography. Powers: High natural charm, infectious stage energy, rapid melodic intuition, and growing competency in digital audio workstation (DAW) track production.

The youngest trainee in the debut line, characterized by genuine sincerity and immense latent potential. His limited physical endurance and vulnerability under intense pre-debut schedules lead to physical collapse, prompting Iwol to implement strict stamina-building and health protocols to safeguard his development. Powers: Rapid learning curve, expressive youthfulness, clean tonal vocal quality, and high choreography adaptability.

An arrogant, deeply corrupt veteran music producer contracted by UA Entertainment. Accustomed to absolute obedience, he attempts to gut Spark’s youth-oriented self-produced concept to impose an outdated, low-effort ballad style designed for personal kickbacks. When challenged, he resorts to verbal degradation, physical violence, and institutional blackmail. Powers: Extensive industry connections, executive leverage within UA Entertainment, and manipulative production control.

An established senior ballad singer under UA Entertainment who conceals an abusive, predatory personality beneath a polished public persona. He systematically exploited and mentally battered Jeong Seongbin for years to ensure Seongbin remained docile and subservient as an uncredited guide-vocalist. Powers: High public seniority, media influence, and deep-seated institutional favoritism within executive circles.